This invention relates to a regenerative type hazardous waste gas fume and odor incinerator that has a flow control valve system between the combustion chamber and the regenerator beds providing for continuous gas flow in one direction, passing through the gas or oil fed combustion burner.
Nearly all waste gas fume incinerators use heat recovery to obtain a high incinerator temperature with less fuel consumption. In general, heat recovery regenerators are more efficient than heat exchangers, and so are preferred for low fuel usage incinerator consumption.
This invention relates to a regenerative type incinerator used to control hazardous waste gas fumes and odors produced by industrial processes. In particular, the invention provides a new and novel construction of the regenerators to improve the ignition or burning of hazardous gases by control of the flow direction through the burner and the combustion zone.
Safety codes require inflammable industrial gas concentrations to be less than one fourth (1/4) of the lower explosion limits, and so industrial process exhaust fumes have a relatively low concentration of combustible gases. These low concentrations are difficult to ignite. It is also hard to keep the purification process combustion going in ignited gases of low concentrations unless high temperatures are maintained until the chemical reactions are completed.
Prior art waste gas fume incinerator apparatus in general follows either one or the other of the following processes:
In the first process, waste gas fumes flow in the same direction continuously through the burner and the combustion chamber. A high temperature heat exchanger of tubular or plate type construction is included in the system to conserve fuel and to increase the incinerator temperature by preheating waste gas fumes before they reach the burner. This process ignites and incinerates waste gas fumes at the burner, in the burner flames, as preheated waste gas passes through the burner from the back of the burner to the front of the burner in the same direction all of the time. In flame fronts and burning flames, gases are at elevated temperatures and highly ionized. Preheated combustible gases flowing into the flames are readily ignited by the highly reactive flame fronts and purified by a half second retention time in the combustion chamber. After leaving the combustion chamber, purified gases enter the opposite side of the high temperature heat exchanger to recover some of the heat released by the burner to reduce the large amount of fuel used in this process.
In the second process, instead of the waste gas passing through burner flames for gas purification the gases are ignited and burned by raising them to very high temperatures, 1500 degrees or higher, and holding all of the gas at such temperatures for at least a half second retention time for the hazardous chemicals to reduce to harmless carbon dioxide and water. This process is called "thermal incineration". Effective thermal incineration apparatus can be designed with very large, expensive, high temperature, high efficiency heat exchangers. However, all practical systems use the regenerative type heat exchanging device. In state of the art regenerative type incinerators gas flow in the combustion chamber reverses direction and cannot be controlled to flow in one direction through the burner and burner flames for early ignition of impure and noxious chemicals. With lack of control in the combustion chamber, to achieve the shortest path retention time of a half second, the combustion chamber is sized for an average 1.8 (one and eight-tenths) second retention time which requires the combustion chamber volume to be inreased to 3.6 (three and six tenths) times in size. The system must use very high temperatures to ignite and burn chemicals and those high temperatures need expensive, high temperature materials for construction of the combustion chamber. The construction cost and the effectiveness of regenerative type incinerators could be improved if the waste gases are ignited as they enter the combustion chamber by passing them through the burner flames.
An example of the Thermal Incineration process is found in the apparatus disclosed in U.S. Pat. No. 3,895,918. In this patent, a thermal regeneration, anti-pollution system has a central, generally cylindrical, purification chamber which operates at a high temperature to oxidize, burn-off, or otherwise, thermally process undesired or noxious fumes or odors from industrial or other processes. The purification chamber is topped by a refractorily-lined dome and at its periphery there are a plurality of associated flue-heat-exchange bed combinations, bounded by vertical walls defining horizontal cross-sections in the general shape of a catenary curve. The heat exchange bed in this patent includes ceramic packing held towards the inner side of the heat exchange bed by angled louvers. A plurality of burners are provided for keeping the temperature in the purification chamber at between 1400 degrees and 1800 degrees Fahrenheit. As was pointed out above, the refractory-lined dome and other high temperature construction materials required by this device sized to accommodate the longer gas retention time makes the cost of such devices prohibitive.